Thin-film transistors (TFTs) are conventionally made by depositing thin films of an active semiconductor layer, a dielectric layer and metallic or conductive contacts over a supporting (but non-conducting) substrate, e.g. silicon, glass, and plastics. These TFTs may act as the “engine” to drive displays, such as liquid crystal displays (LCDs). TFTs can be embedded within the display panel, for example to reduce crosstalk between pixels, improve image stability, and achieve desired video speeds.
Conventional TFTs are constructed with inorganic semiconducting materials to form the channel. These materials have an electron mobility of a-Si<indium gallium zinc oxide (IGZO)<p-Si. The inorganic materials work well in a static state. However, when used in a switching state for simple electronic or display applications at reasonable speeds, the performance is poor.
On the other hand, organic semiconducting materials have emerged which may be used in the fabrication of TFTs. Advantages of organic thin film transistors (OTFTs), such as organic field effect transistors (OFETs), may include elasticity, low temperature processing, and/or chemical stability. These characteristics result in product flexibility, novel processes, and novel substrates. However, OTFTs present some challenges such as low electron mobility or hole mobility. Mobility depends upon the contact resistance, interlayer structure, and process method.